Making mosquitoes completely free of parasites is essential to preventing malaria

New study indicates future path for malaria research - News Release

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0100 hours GMT
Friday 28 December 2007
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Making sure mosquitoes are completely free from malaria parasites is one of the more effective ways to fight the transmission of malaria, says new research published today (Friday 28 December) in PLoS Pathogens.

The new study indicates that simply reducing the number of parasites inside mosquitoes may not cause the desired decrease in malaria transmission. Researchers previously thought that reducing the number of parasites within mosquitoes would reduce transmission to humans, but the new research shows that even mosquitoes with dramatically reduced numbers of parasites inside them are capable of infecting people. Therefore the parasites need to be completely eliminated from each mosquito in order to fully prevent transmission to humans.

The new study was led by Professor Bob Sinden from Imperial College London's Department of Life Sciences. He worked with colleagues in the Department of Infectious Disease Epidemiology to perform new analyses of the malaria parasite's growth and multiplication inside the body of a mosquito.

When mosquitoes feed on the blood of an infected human, the malaria parasites undergo complex development in the insect's gut. It takes between 10 and 20 days of growth and development within the mosquito before the disease can be transmitted to another person when the mosquito takes another blood meal.

Mathematical analyses in the new study found that at any stage in the developmental life cycle of the parasite, the more parasites are present, the less efficient their growth and development.

Professor Sinden explains: "In other words, we found that the parasites' development inside a mosquito host becomes less and less successful the more developing parasites are present. Essentially, this means that the level of parasite infection inside the mosquito is not what we need to tackle, because a mosquito with, for instance, 50 parasites inside may not be substantially more infectious than a mosquito carrying only 5 parasites, so it is that last few parasites that we must eliminate. Luckily in many parts of the world each mosquito may carry as few as five parasites."

Professor Sinden said that the results of the study were of great importance for the malaria research field, giving a clear indication of where scientists need to concentrate their research efforts with the aim of preventing the transmission of malaria in the future.

"It is clear now that it will not be sufficient to develop techniques which get rid of 'most' of the malaria parasites inside a mosquito. We now know that the most important challenge for research in this area is to refine techniques so we reduce the number of mosquitoes that have any parasites in them whatsoever," he said.

Each year, there are 300 million to 500 million cases of malaria throughout the world and about 1 million child deaths. In areas where malaria is common, such as sub-Saharan Africa, it can be the leading cause of death and poor growth among young children.

-Ends-

For more information please contact:

Danielle Reeves
Imperial College London Press Office,
Tel: +44 (0)20 7594 2198
Mob: +44 (0)7803 886248
Email: Danielle.reeves@imperial.ac.uk

Notes to Editors:

1. 'Progression of Plasmodium berghei through Anopheles stephensi Is Density-Dependent' PLoS Pathogens, 28 December 2007.

Robert E. Sinden1 (1), Emma J. Dawes (2), Yasmene Alavi (1), Joanna Waldock (1), Olivia Finney (1), Jacqui Mendoza (1), Geoff A. Butcher (1), Laura Andrews (3), Adrian V. Hill (3), Sarah C. Gilbert (3), Maria-Gloria Basanez (2).

(1) Division of Cell and Molecular Biology, Faculty of Life Sciences, Imperial College London, London, United Kingdom.
(2) Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, London, United Kingdom.
(3) Wellcome Trust Centre for Human Genetics, University of Oxford, United Kingdom.

2. About Imperial College London

Rated as the world's fifth best university in the 2007 Times Higher Education Supplement University Rankings, Imperial College London is a science-based institution with a reputation for excellence in teaching and research that attracts over 12,000 students and 6,000 staff of the highest international quality.

Innovative research at the College explores the interface between science, medicine, engineering and management and delivers practical solutions that improve quality of life and the environment - underpinned by a dynamic enterprise culture.

With 66 Fellows of the Royal Society among our current academic staff and distinguished past members of the College including 14 Nobel Laureates and two Fields Medallists, Imperial's contribution to society has been immense. Inventions and innovations include the discovery of penicillin, the development of holography and the foundations of fibre optics. This commitment to the application of our research for the benefit of all continues today with current focuses including interdisciplinary collaborations to tackle climate change and mathematical modelling to predict and control the spread of infectious diseases.

The College's 100 years of living science will be celebrated throughout 2007 with a range of events to mark the Centenary of the signing of Imperial's founding charter on 8 July 1907.

Website: www.imperial.ac.uk